Here's what it is.
There are certain aspects of life that just are not meant to be defined by words. You know what it is when you encounter it, but it works on a level words can't touch.
The whole concept of "cool" is like that. In fact, cool is so cool that dictionaries often use the word itself to attempt to describe it. "Socially adept" doesn't quite cut it. A lot of people describe themselves as "cool", but those are people who don't have a clue as to what cool is. The people who are cool are, well, too cool to label themselves that way. When you're cool, other people already know it, so there's no need speak of it.
Miles Davis never said he was cool. His music said it all.
Cool and Collected is something of a sound bite in relation to how his music defined jazz in the latter half of the twentieth century. But what a sound bite it is! Focusing mostly on the work he did in the mid- to late-'50s with various incarnations of the Miles Davis Quintet, this compilation showcases some of the tunes that made Miles Davis the epitome of cool. "So What", arguably the tune that veered jazz away from bebop toward a more modal style, appropriately opens the album. In this 1959 version, Cannonball Adderly on alto sax and John Coltrane on tenor sax are also featured, as well as Bill Evans on piano, bassist Paul Chambers, and drummer Johnny Cobb.
Much of Cool and Collected centers around the triumvirate of Davis, Coltrane, and Adderly. "Milestones," "Stella By Starlight," and "Fran-Dance" all showcase the three horn players bouncing scales off each other, and the interplay between them, nearly forty years later, still astounds. Between those four pieces alone, there's nearly 25 minutes of trumpet and sax swirling and dipping like the aural equivalents of birds at play.